Does blood sampling from caudal vessels in fish produce parameter values different from those obtained by heart puncture?

Analyses of blood samples in ichthyology are of importance for assessment of fish health as well as fish responses to environmental stressors. The measurement results may be affected by multiple factors. This study aimed at assessment of the influence of the blood collection site by comparing dual values of indices measured in samples obtained both from the heart and puncturing caudal vessels in the same fish specimens. Our results revealed that the sampling site did not significantly influence measured variables including haematological indices, the plasma biochemistry profile, acid-base balance parameters and the phagocytic activity. To conclude, for the rainbow trout (Oncorhynchus mykiss) both sampling methods are interchangeable with regard to the above-mentioned indices.